This invention relates to the testing of a system which includes receiving and transmitting circuitry located in close proximity to each other, as in a telephone, and, in particular, to the concurrent testing of the receive and transmit circuitry.
A problem present in the prior art may be best explained with reference to FIG. 1 which shows a device under test (DUT) 10. DUT 10 includes a receive section 12, a transmit section 14 and a lock-out circuit 16 designed to prevent oscillations due to feedback between the transmit and receive sections. Circuitry 12, 14, 16 may be mounted on a printed circuit board for subsequent installation in a telephone.
Receive section 12 includes an input circuit 121, amplifying and processing circuitry 122 and 123, and a digital-to-analog (D/A) converter circuit 124. The output 125 of the A/D converter 124 is intended to be supplied via output lines 127 and 128 to a speaker 20. The speaker 20 converts the analog signals it receives into audio signals.
A microphone 30 converts incoming audio signals into analog signals which are supplied via lines 137 and 138 to the input 140 of transmit section 14. The input 140 of transmit section 14 is applied to an input circuit 141 whose output is supplied to amplifying and processing circuitry 142 and 143. The output of circuit 143 is applied to an analog to digital (A/D) converter circuit 144 having an output 145 and two output lines 147, 148.
Lock-out circuit 16 includes: (a) circuitry responsive to signals being processed and propagated along the receive section 12 to prevent and inhibit the processing and propagation of signals along the transmit section 14; and (b) circuitry responsive to signals being processed and propagated along the transmit section 14 to prevent and inhibit the processing and propagation of signals along the receive section 12. Lock-out circuit 16 may be a sophisticated computer algorithm generated and driven by appropriate sensors. Lock out circuit 16 prevents the testing of sections 12 and 14 at the same time. Comparator 43 may be a sophisticated computer algorithm generated by tester 40.
The DUT may be exercised and tested by means of a tester 40 which includes: (a) a digital tone generator (DTG) 41, for supplying digital test signals via lines 117 and 118 to the input of the receive section 12; (b) analog-to-digital (A/D) circuitry 42 for sensing the analog signals produced at the output 125 of the receive section 12 and converting these analog signals to corresponding digital signals; and (c) comparator circuitry 43 for comparing the digital signals supplied to receive system 12 with those received from the output of section 12 to determine the operability of receive section 12. Tester 40 also includes: (a) a digital tone generator (DTG) 41a (which may be part of DTG 41) for generating signals to be applied to the transmit section; (b) a digital-to-analog (D/A) circuit 44, responsive to DTG 41a, for supplying analog signals to the input 140 of transmit section 14; and (c) comparator means 45 for sensing the digital signals produced at the output (145) of transmit section 14 and for comparing the digital signals received from the transmit section with the digital signals supplied (via D/A 44) to the input of the transmit section. Comparator 45, like comparator 43, may be a sophisticated computer algorithm generated by the tester.
As noted above, due to the presence of lock out circuit 16, each one of sections 12 and 14 has to be tested separately. Due to the integrated design of the receive, transmit and lock-out sections, the lock out circuitry 16 can not be easily disabled during testing of the receive and transmit circuitry in DUT 10.
Thus, in accordance with the prior art, sections 12 and 14 have to be tested separately one at a time. This is necessary since whenever one section is processing signals, it inhibits the other section from processing signals. However, it should be evident that this causes the testing of the receive and transmit channels to be inefficient.
Also, in the prior art system of FIG. 1, there is no mechanism provided to test the receive channel with its speaker and the transmit channel with its microphone, all at the same time.
The present invention resolves the defects and disadvantages discussed above.